linux-kernel - Re: [RFC PATCH 1/1] seccomp: provide information about the previous syscall

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Message-ID: <20160122173050.GE9608@ast-mbp.thefacebook.com>
Date:	Fri, 22 Jan 2016 09:30:50 -0800
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp>
Cc:	keescook@...omium.org, luto@...capital.net, wad@...omium.org,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	kernel-hardening@...ts.openwall.com
Subject: Re: [RFC PATCH 1/1] seccomp: provide information about the previous
 syscall

On Fri, Jan 22, 2016 at 03:30:00PM +0900, Daniel Sangorrin wrote:
> This patch allows applications to restrict the order in which
> its system calls may be requested. In order to do that, we
> provide seccomp-BPF scripts with information about the
> previous system call requested.
> 
> An example use case consists of detecting (and stopping) return
> oriented attacks that disturb the normal execution flow of
> a user program.
> 
> Signed-off-by: Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp>
...
> diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
...
>  struct seccomp_data {
>  	int nr;
> +	int prev_nr;
>  	__u32 arch;
>  	__u64 instruction_pointer;
>  	__u64 args[6];

this will break abi for existing seccomp programs.
New field has to be at the end.